TY  - JOUR
A1  - Powali, Debarchan
A1  - Sharma, Shubham
A1  - Mandal, Riddhi
A1  - Mitra, Supriyo
T1  - A reappraisal of the 2005 Kashmir (M-w 7.6) earthquake and its aftershocks
BT  - seismotectonics of NW Himalaya
JF  - Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth
N2  - We study the source properties of the 2005 Kashmir earthquake and its aftershocks to unravel the seismotectonics of the NW Himalayan syntaxis. The mainshock and larger aftershocks have been simultaneously relocated using phase data. We use back-projection of high-frequency energy from multiple teleseismic arrays to model the spatio-temporal evolution of the mainshock rupture. Our analysis reveal a bilateral rupture, which initially propagated SE and then NW of the epicenter, with an average rupture velocity of similar to 2 km s(-1). The area of maximum energy release is parallel to and bound by the surface rupture. Incorporating rupture propagation and velocity, we model the mainshock as a line source using P- and SH-waveform inversion. Our result confirms that the mainshock occurred on a NE dipping (similar to 35 degrees) fault plane, with centroid depth of similar to 10 km. Integrated source time function show that majority of the energy was released in the first similar to 20 s, and was confined above the hypocenter. From waveform inverted fault dimension and seismic moment, we argue that the mainshock had an additional similar to 25 km blind rupture beyond the NW Himalayan syntaxis. Combining this with findings from previous studies, we conjecture that the blind rupture propagated NW of the syntaxis underneath a weak detachment overlain by infra-Cambrian salt layer, and terminated in a wedge thrust. All moderate-to-large aftershocks, NW of the mainshock rupture, are concentrated at the edge of the blind rupture termination. Source modeling of these aftershocks reveal thrust mechanism with centroid depths of 2-10 km, and fault planes oriented subparallel to the mainshock rupture. To study the influence of mainshock rupture on aftershock occurrence, we compute Coulomb failure stress on aftershock faults. All these aftershocks lie in the positive Coulomb stress change region. This suggest that the aftershocks have been triggered by either co-seismic or post-seismic slip on the mainshock fault.
KW  - Kashmir earthquake
KW  - Aftershocks
KW  - High frequency back-projection
KW  - Source
KW  - mechanism
KW  - Coulomb failure stress
KW  - Seismo-tectonics
Y1  - 2020
U6  - https://doi.org/10.1016/j.tecto.2020.228501
SN  - 0040-1951
SN  - 1879-3266
VL  - 789
PB  - Elsevier
CY  - Amsterdam
ER  -